missing model number need it

i gotta customers tablet with video problems and i cannot locate the model number because the sticker is missing... is there somewhere i can find the number inside the tablet?
the video doesnt work so cant get into the os...

First plug in an external Monitor and try that to see if you get a picture.

Depending on the laptop, look for a F Key with a small screen on it, use that and either shift,Ctrl or Alt to switch to an external screen, these are usually toggle switches so do it again and you revert to the in-built screen.

If that works download SIW.EXE which is stands for System Information Windows
(Diagnostic tool) and look under Software, or BELARC will give similar results but a easier to understand layout,with less info.